JP-A-2009-129384 discloses a method of calculating a charging fee to charge an electric vehicle. In the method, an authentication process to allow the charging is performed based on identification (ID) card such as a driver's license card or the like. The amount of electricity used to charge the electric vehicle at home and the amount of electricity used to charge the electric vehicle at an external charging apparatus installed at, for example, a super market, a department store, a parking area, or a gas station are separately stored in a database of a system of an electric power company. The charging fee for the amount of electricity used at home and at the charging station are calculated based on the type of a contact between a user and the power company and then collectively charged to the user.
In the conventional method, the charging apparatus needs to send user ID information, which identifies a user who uses the charging apparatus to charge the electric vehicle, and electricity usage data, which indicates the amount of electricity used in the charging apparatus to charge the electric vehicle, to the system of the power company. That is, the conventional method requires that every charging apparatus has a communication function to communicate with the system of the power company. Therefore, the cost of manufacturing and installing the charging apparatus may be increased, and a place where the charging apparatus is installed may be limited. As a result, the widespread use of the charging apparatus 30 may be hindered.